docs: def parse_start_date(self, request):
          """
          Return start date for event occurrences, which is one of the following
          in order of priority:
           - `start_date` GET parameter value, if given and valid
           - page's `default_start_date` if set
           - today's date
          """
          if request.GET.get('start_date'):
              try:
                  return djtz.parse('%s 00:00' % request.GET.get('start_date'))
              except ValueError:
                  pass
          return self.default_start_date or djtz.midnight()